A hydraulic circuit of a construction machine including center bypass passages, into which a pressurized oil from hydraulic pumps is supplied, includes a directional control valve group in tandem with the center bypass passages; a bleed-off valve on a downstream side of each center bypass passage; and a merging circuit that merges the pressurized oil supplied into one center bypass passage and that in another center bypass passage, wherein each directional control valve includes a first internal passage that flows the pressurized oil into the center bypass passages, and a second internal passage that supplies the pressurized oil to a hydraulic actuator, wherein the center bypass passages and the first internal passage form a parallel passage, wherein an opening area of the bleed-off valve is changed, wherein the merging circuit includes a merging directional control valve that controls an inflow direction of the pressurized oil to be merged.